What is it about a full moon that makes people do crazy things and commit crimes?

The full moon has no effect on human or wolf behavior. Public Domain Image, source: USFWS.

There are no statistically significant records indicating any connection between crime waves or full hospitals and the full moon, according to the National Geographic News. This misunderstanding perhaps has its source in a long line of mythology. Werewolves were said to be humans that turned into wolves during the full moon. The sophisticated culture of today perhaps modernized this myth to say that people only act like wolves during full moons, but don't actually turn into wolves. The werewolf myth has its roots in another myth; the belief that real wolves howl at the full moon but not at any other kind of moon. This particular belief, which is scientifically false, traces all the way back to the mythology of the Greek and Roman gods.

The moon's gravity is strong enough to help cause the ocean tides, but too weak to do much else. Weak forces only produce significant effects when there is a lot of material to act on. In the case of the moon, the immense size of the oceans and their fluid nature makes the weak gravity of the moon add up to significant effects in the form of tides. In contrast, humans are so small compared to the oceans, that the effect of the moon's gravity on humans is negligible. Even if the moon's gravity was strong enough to affect humans, it would do nothing more than make us slightly heavier or lighter. Gravity is just a force that pulls on mass. Gravity does nothing mystical or psychological to the objects it acts on.